Javadoc
Returns the key to use in the presenceMap for a fully qualified xmpp ID. The roster
can contain any valid address format such us "domain/resource", "user@domain" or
"user@domain/resource". If the roster contains an entry associated with the fully qualified
xmpp ID then use the fully qualified xmpp ID as the key in presenceMap, otherwise use the
bare address. Note: When the key in presenceMap is a fully qualified xmpp ID, the
userPresences is useless since it will always contain one entry for the user.